/**
 * 特殊类型
 * @flow
 */

 const a: "foo" = "foo"
 const type: "success" | "warring" | "fail" = "fail"

//  定义类型
type stringAndnumber = string | number

const gg: stringAndnumber = 12312

// maybe 类型
// const gender: ?number = 1231 // ===>
const gender: number | null | void = 1231